void main(List<String> args) {
  List<String> xxxList = ['1',  '2',  '{}'];

  Map<String, int> zs =  {
    '123': 100,
  };

  zs.forEach((key, value) {

  });

  sayHello(123);

  
}


// 泛型函数
T sayHello<T>(T name){
  return name;
}